LG&E/KU – Ghent Station Phase II Air Quality Control Study Fly Ash Handlingpsc.ky.gov/pscscf/2011 cases/2011-00162/20110616... · 2011-05-25 · LG&E/KU – Ghent Station System

LG&E/KU – Ghent Station Phase II Air Quality Control Study Fly Ash Handling March 18, 2011 Revision B – Issued For Client Review B&V File Number 41.0814.5

LG&E/KU – Ghent Station Fly Ash Handling Table of Contents

Table of Contents

1.0 Introduction.......................................................................................................... 1-2

2.0 System Description and Evaluation ..................................................................... 2-1

2.1 Description and Capacity of In-Place Systems........................................ 2-1

2.2 New Fly Ash Loading.............................................................................. 2-2

3.0 Summary .............................................................................................................. 3-1

Appendix A In service Dry Ash Handling Arrangement Drawings

Appendix B Reference Drawings

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LG&E/KU – Ghent Station Fly Ash Handling Introduction

1.0 Introduction

The amount of particulate matter collected from the exhaust gas from all four

units at Ghent will be increased by the additions and modifications proposed by the Air

Quality Control (AQC) Study Phase II. At the time of this report, design modifications

are underway to convert the existing fly ash handling system at Ghent Station from a

sluice system to a dry conveying system. For purposes of this report, the modifications to

the ash handling system(s) that collect and transport particulate to the ash handling

facility will be assumed as in place and operational. It is the modified system that will be

investigated to confirm acceptability under the new operating conditions identified in the

AQC Phase II Study. The purpose of this report is to describe the modified fly ash

handling system and its operating capacity, quantify the impacts to the system due to the

AQC modifications proposed, and confirm its acceptability or identify any modifications

required to allow proper operation.

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LG&E/KU – Ghent Station System Description and Fly Ash Handling Evaluation

2.0 System Description and Evaluation

All four units at Ghent currently include an electrostatic precipitator (ESP) for

collection of particulate matter from the unit exhaust gas stream. As part of the AQC

modifications proposed by Phase II, the existing ESPs will be supplemented or replaced

at all four units by pulse jet fabric filters (PJFFs) to collect fly ash prior to the exhaust gas

reaching the wet scrubbers. Sorbent is currently being injected into the AQCS systems at

Units 1, 3, and 4 for SO3 control. Phase II proposes the injection of sorbent, either lime

or trona, to Unit 2 as well, and powdered activated carbon (PAC) for mercury control at

all four units. In addition to the ash, the injected adsorbent particulate must also be

removed from the exhaust streams by the PJFFs.

For purposes of this study all particulate removed from the exhaust gas will be

covered under the term “fly ash.” The amount of total fly ash that must be handled after

the system improvements will be higher at each unit than that currently processed

through the system for the following reasons.

Improved efficiency of the proposed PJFF over the ESP

New injected particulate material that must be removed from the gas

stream.

This increased load on the existing fly ash handling system must be evaluated and

any recommended modifications or operating conditions identified.

2.1 Description and Capacity of In-Place Systems

The existing fly ash system conveys fly ash from the ESPs at all four units and air

heater ash from Unit 1 by a wet sluice (Hydroveyor) system to nearby ash ponds. The

economizer ash for Units 1 and 2 is also sluiced with the fly ash by the Hydroveyor

system.. Unit 3 and 4 economizer ash is collected in wet tanks and sluiced with bottom

ash and pyrites to the ash ponds. The design conveying rates are indicated below in

Table 2-1.

The Ghent Station is currently injecting lime and trona into the exhaust stream of

three of the four units. Product is injected both upstream and downstream of the ESPs,

but for the purposes of the study, it is conservatively being considered as conveyed by the

existing fly ash handling systems. The current values are also indicated in Table 2-1.

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Table 2-1 Existing Fly Ash and Sorbent Flow Rates

Parameters Unit 1 Unit 2 Unit 3 Unit 4 Total Fly Ash and hopper ash design rates, tons/hour

27 28 30 30

Lime tons/hour 1.5 1 0 0 Trona, tons/hour 1.75 0 2 3

Total 30.25 29 32 33 124.25

Subsequent to the wet to dry system upgrades at Ghent, fly ash from the ESPs will

be collected and transferred as dry material. This dry ash system is expected to be in-

place and operational at the beginning of the Phase II work. Fly ash collected by the

fields in the ESPs will fall to collection hoppers at the bottom of the ESP. Duct hopper

ash from air heaters and economizers collects in hoppers associated with these collection

points. Mechanical exhausters will create a vacuum in piping connected to the hopper

bottoms. Collected ash will be transferred under vacuum from the hoppers to a

filter/separator where the collected ash will be subsequently transferred by a pressurized

pneumatic blower system to the ash storage and loadout silos at the coal combustion

residue (CCR) facility south of Highway 42. At the CCR facility ash will be either

unloaded from the silos to trucks for transfer to beneficial reuse or deposited on

conveyors for landfilling operations.

Each unit will be provided with its own vacuum piping and mechanical exhauster

system that transfers ash from the collection hoppers to the appropriate filter/separator.

The Unit 1 and Unit 2 filter separators and associated pressure blowers will be housed in

a common fly ash equipment building located on the north side of Unit 2. The Unit 3 and

Unit 4 fly ash equipment building will be located to the north and west of Unit 4.

The general location of the dry fly ash system equipment buildings are shown on

Sketch A in Appendix A.

2.2 New Fly Ash Loading The new equipment proposed in the Stage II study will introduce three additional

sources of particulate to be added to the load currently being processed by the existing

systems: additional fly ash, lime or trona and PAC.

New PJFFs will be installed downstream of the existing ESPs at Units 1, 2, 3, and

4 and the ESPs may remain in operation depending on the AQCS technologies used. The

new PJFFs will be designed based on a theoretical PM limit of 0.01 lb/MBtu, a somewhat

greater efficiency than the existing ESPs, resulting in the PJFFs collecting additional fly

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ash beyond that collected by the ESP. For the purposes of this evaluation, all the ash

generated in the boiler will be considered as fly ash.

To provide additional SO3 control, sorbent (trona) injection systems have already

been installed at Units 1, 3, and 4 as indicated above in Table 2-1. A new trona or lime

injection system will be installed at for all units as part of the Phase II modifications

proposed. The addition of sorbent injection will result in additional particulate being

captured by the new PJFFs. The additional reacted and un-reacted lime or trona must be

considered as a new PM load to be processed with the fly ash.

For mercury control, PAC will be injected into the exhaust stream upstream of

each PJFF (all four units). Similar to the sorbent, the PAC is then collected in the PJFF

for processing as additional ash load at each unit.

The total particulate to be captured by the PJFF for each unit is summarized in

Table 2-2.

Table 2-2 Particulate to be Collected at PJFFs

Parameters Unit 1 Unit 2 Unit 3 Unit 4 Total Fly Ash, tons/hour 25.5 28.5 28.6 30.1 PAC, tons/hour 0.6 0.6 0.7 0.6 Trona, tons/hour 1.6 2.5 2.5 2.5

lime, tons/hour 2.1 3.3 3.3 3.3 Total (using the worst case lime or Trona rate.)

28.2 32.4 32.6 34.0

Because these planned adsorbent flow rates represent a relatively small increase

in design flow rates, they have been used in as the design flow rates for the dry ash

conversion system design. Thus, the in-place systems will be capable of handling the

expected adsorbents loading if the system and piping can be configured to include the

new PJFFs.

The vacuum piping system at each unit could be extended to the new pickup

points at the bottom of new PJFF hoppers, using the existing mechanical exhausters to

maintain the vacuum. The particulate collected in the hoppers will be forwarded to the

silos. The feasibility of this approach is dependent on whether the vacuum systems are

capable of conveying the required distances. The proposed fabric filter arrangements are

indicated in Site Arrangement Drawings 168908-GCDS-1001 and 1002 referenced in

Appendix B. The location of the Units 1 and 2 PJFFs are adjacent to the Unit 1 and 2 ash

handling equipment buildings shown in Drawing 172150-CASB-G1001 in Appendix A.

Accordingly, the system will be able to convey from either the ESP or the PJFFs.

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March 2011 2-4 168908.41.0814.5

Similarly, the planned location for the Unit 4 PJFFs is shown near the location of the

Units 3 and 4 ash handling building as shown in Drawing 172150-CASB-G1002 in

Appendix A. The Unit 3 PJFF is located significantly farther from the Units 3 and 4 ash

handling building than the Unit 3 ESP. Consequently, the vacuum system designed for

conveying from the ESP is not expected to be able to convey the ash the increased

distance. A new ash conveying system will need to be installed to convey the ash and

sorbent from the Unit 3 PJFF to the storage silos. For the purposes of the study, a dilute-

phase pressure conveying system will be used. The PJFF hoppers will require about 15

feet clearance for the pressure feeder vessels. The new dilute-phase transfer system will

be sized to transfer all collected fly ash from the 100% capacity PJFF should the existing

Unit 3 ESPs ultimately be removed from service. The new equipment will be located

beneath the Unit 3 PJFF and is shown on Drawing 168908-GCDS-1001 as Item 8. Costs

for this system are included in the overall cost estimate for Ghent Unit 3. The cost of

extending the existing system to the hopper area of the new PJFFs at Units 1, 2, and 4 are

included in those cost estimates, respectively.

LG&E/KU – Ghent Station Fly Ash Handling Summary

3.0 Summary

Based on the evaluations presented in Section 2, the following recommendations

are made with regard to fly ash handling systems for the four units at Ghent Station. For

purposes of this report, the modifications to the ash handling system(s) currently

underway at all four Ghent units are assumed as in place and operational. The

recommendations below are subject to confirmation during detailed design.

Unit 1 – rework the existing Unit 1 vacuum exhauster system to extend the

piping to the hoppers at the new Unit 1 PJFF. The piping will be sized

and arranged to allow the use of the PJFF to collect all particulate should

the ESPs be taken out of service at some future time. The vacuum system

will convey the ash to the in-use filter/separators. The ash will be pressure

conveyed to the in-use silos located in the CCR facility south of Highway

42.







42.

Unit 3 –add a new pressure conveying ash handling system to forward all

collected fly ash from the Unit 3 PJFF to the in-use silos located in the

CCR facility south of Highway 42. The system will require feeder vessels

under each hopper, pressure blowers, and two abrasion resistant alloy pipe

lines routed on the in-use pipe rack across Highway 42. The new system

will be sized to allow the use of the PJFF to collect all particulate should

the ESPs be taken out of service at some future time.







42.

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LG&E/KU – Ghent Station Fly Ash Handling Appendix A

Appendix A

In service Dry Ash Handling

Arrangement Drawings

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Ghent CCR Transport Site Arrangement

Existing Plant – East End

Drawing No. 172150-CASB-G1001

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March 2011 A-3 168908.41.0814.5

Ghent CCR Transport Site Arrangement

Existing Plant – West End

Drawing No. 172150-CASB-1002

LG&E/KU – Ghent Station Fly Ash Handling Appendix B

Appendix B

Reference Drawings

168908-GCDS-1001 Site Arrangement Unit 1 and Unit 2 168908-GCDS-1002 Site Arrangement Unit 3 and Unit 4

March 2011 B-1 168908.41.0814.5

Documents

LG&E/KU – Ghent Station Phase II Air Quality Control Study Fly Ash Handlingpsc.ky.gov/pscscf/2011 cases/2011-00162/20110616... · 2011-05-25 · LG&E/KU – Ghent Station System